Ignition device.



G. S. HOLLISTER. IGNITION DEVICE. I'IPI-LICATION FILED APR.24, 1915.

Patented Hay l, 1917.

MANUFACTUMNG Comenius, el

MASSCHUSETTS.

application allee april 1J.'

To all lwhom t may concern.

Be it known that I, Grenen S. llonnisrnu.y a citizen of the United States, residing at .Allston7 Boston, in the county of Su "olli 5 and State of ll'lassachusetts, have inve teil certain new and useful improvements in ignition Devices; and I' do hereby declare the following- Ato be a full, clear, and exact description of the inventionsuch as will l enable. others skilled in the art to 'which it appertains to make and use the same.

The present invention relates to ignition devices for internal combustion niotors7 and inore particularly to spark plugs einplo'vetl.

i for ignitingY a charge oiE explosive gas.

It is desirable that the spark plugs cniployetl with internal combustion motors shall he so constructed that they will open ate indefinitely without short circuit-ing clue 0 to carbon or lubricating oil bridging the spark gap, or to a leakage of oil which permits the fiow or" current from the high te sion electrode to the outer metal shell. of the plug. f

An oloject of the present invention is to provide a spark plug having,` an iinproverl construction and mode of operation in order to insure that the plug shall operate satisfactorily for an' indefinite period without liability of a short Circuit by oil, carbon, or

other foreign material.

With this object in viei/ the several ieatures ot the invention consist iu certain. novel features o'constructioin combinations :nul arrangements of parts hereinafter lcscrihecl and claimed, the ailvantages of which will he obvious to those skille l in the art from the following description.

In the aceonipan ving` drawings illustrating the preferred forni ot the inventio g Figure l represents a. longitudinal sec-tion in` elevation of the improvecl spark plug;

Fig 2 is a bottom plan vieiv oi: the plug; .5 shown in Fig l; Fig. 3 is a (letail showing;

an elevation of the lower portion oit ne plug; Fig. 4 is an elevation par iv in sec-- tion of a modified form of s iark i ug; and

Fig. 5 is a botten/1 plan view of the pl 50 shrown in Fig. li.

lhe spark plug,r shown in the illustrated embodiment of the invention consists of an outer metal shell l having an annular sin 2 which is threadedly received in 'the vl der of the internal combustion motor.

usual high tension eleotroe 5 is mounten i Specification ef Letters Patent.'

`provi ling a plurality7 ol*l electrodes successively receive the spa k, thus causin a. porcelain bushing 6 and is connec upper enel with a terininal cap T. insulator 1bushing,` ti is secured to the nietal shell hy a gland 8 threarleilly engaging with the nietal shell and -lclingly clampingl bushing in the shell tarougli copper a. ii: tos .vashers 9. The porcelain hushiug'is n vicled with a c unil-eiela re l recess in which the lower end oi" the lii i tension electrmiiefexgtcmls to torni a sparking ioint. lt frequently happen-s that a consiilei'ahlo quantitav of lubricating' oil may collect upon the lower portion the spark plug;- andV electrodes and he consunictl oy ille e.\;plosion ot gas in the roinhus-ion clniinhnr leaving;` carbon ilcposit upon the plu. teinpts have heen inzule to prcvcn o .3 circuiting of the pl H" hv oil or carbon liv either preventin;T le initial acruniulation oi' the oil or carbon upon the phig7 or hv so constructingthe plug: that this acc1unulation oit' arhon or oilL will not prevci passing; oa spark. lu he present invention the formation ot spark insurctl by L. a spark to he itornietl even tlongh the spark gap hetivcei a single pair he temporarily hric1v i To this eiul a low cured to the metal r i inte nieifliate electron interi seri path oit' the spark between the l ign an tension elet @reales te intercep; 1 from the high tension electrode an( it l o the low tension electrotlc. sion elec olle indient' l at il" is soci ..1

tl i and :in internieeiaVL riin of the shell electrode l2? is seein-eil to the insulatii the sparking` points i'orinoil upon the 'il in eleelrorlc 5 angl low tension electroce li. The low .vision ictrode is sh.. such a inannci: that it maj,v he iiri "he saine tiinc ends of the electrode to the shell with the peak of the W arranged to receive the spark. The intermediate electrode is provided with an upwardly bent portion 14 which extends in the direction of the spark gap to provide for the draining of oil from the two sparking points of the electrode, as shown clearly in Fig. l.

It is desirable to prevent the leakage of oil between the high tension electrode and the insulating bushing and consequent short circuiting of the plug and to further provide a tight joint between the electrode and bushing. 'lort'his end each ot the electrodes 5 and 12 is provided with an insulating shell 15 oi mica which is received closely in the recess formed in the insulating bushing, and a s al 16 of permanently flexible cement is received in the eounterbored" portion ot the recess surroumling the electrode, as shown clearly in Fig. l. This cement prevents the passage otl gas from the combustion chamber between the electrode and insulating bushing and due to its permanent llexibilitv permits the relative movement ot` the electrode and blvlshing owing to dili'ercnt eo-ellicients of expansion without destroying the seal.

In the modified forni ot' spark plug shown in Figs. 4 and 5 the insulating bushing is provided with a cent 'al recess 17 and a high tension electrode 18 extending into the recess. The intermediate electrode is formed by a metal ring 20 secured to the lower face of the bushing'by pins 2l and arranged to receive the spark from the high tension elecA trede. The spark is received from the ring 2O by a plurality of electrodes 22- seeured in the riin of the metal shell agidhaving npwardly bent portions 23 to form the sparking points, as shown clearly in Fig. l. NV ith this construction, the spark is `formed between the high tension electrode and the metal ring and between the metal ring and the .low tension electrode secured to the metal shell.

While it is preferred to employ the speeiiic construction and arrangement ot.' parts` shown and described7 it will be understood that this construction and arrangement is not essential except so fa as speeilied in the claim, and may be changed or modified withont. departing from the broader features of the invention.

The invention having been described, what is claimed is z- A spark plug comprising a` metal shell, an insulating bushing secured in the shell7 a high tension electrodo supported in the bushing7 an annular ring secured to the bushing and surrounding the lower portion oi' the high ten-sion electrode, and a plurality of low tension electrodes secured to the shell and having upwardly bent portions arranged to receive the spark from the annular ring. 

